Name: radiation pressure in light and comets
Uploaded: 2023-04-30T12:46:50.000Z
Duration: 1 min 20 s
Channel: JoVE

K12 Standards

Pennsylvania State Academic Standards

9-12

Earth and Space Science

Earth's Systems

3.3.9-12.H

Momentum And Radiation Pressure

Fale elektromagnetyczne przenoszą pęd podczas podróży w przestrzeni. Odpowiednia gęstość pędu jest wyrażona w postaci wielkości wektora Poyntinga i prędkości światła.
Podstawiając objętość zajmowaną przez falę, która przechodzi przez obszar w krótkim odstępie czasu, można uzyskać natężenie przepływu pędu na jednostkę powierzchni.
Średnią szybkość przenoszenia pędu na jednostkę powierzchni uzyskuje się przez zastąpienie średniej wartości wektora Poyntinga intensywnością.
Ze względu na przenoszenie pędu fale elektromagnetyczne wywierają nacisk na powierzchnię, znany jako ciśnienie promieniowania.
Teraz średnia szybkość zmiany pędu jest równa średniej sile i sile na jednostkę powierzchni to ciśnienie promieniowania.
Zatem ciśnienie promieniowania jest wprost proporcjonalne do intensywności fali.
Jeśli powierzchnia doskonale pochłania falę elektromagnetyczną, odpowiedni pęd jest również całkowicie przenoszony na powierzchnię.
Aby uzyskać idealnie odbijającą powierzchnię, zmiana pędu będzie podwójna. W ten sposób podwaja się również ciśnienie promieniowania.

<ol>
	<li>Protokół OpenStax. (2019). Fizyka uniwersytecka Vol. 2. [Wersja internetowa]. Pobrane z <a href="https://openstax.org/books/university-physics-volume-2/pages/16-4-momentum-and-radiation-pressure">16.4 Pęd i ciśnienie promieniowania - Fizyka uniwersytecka Tom 2 | Protokół OpenStax</a></li>
</ol>

pęd i ciśnienie promieniowania

Na obiekt pochłaniający falę elektromagnetyczną działa siła skierowana w kierunku rozchodzenia się fali. Siła ta występuje, ponieważ fale elektromagnetyczne zawierają i przenoszą pęd. Siła ta uwzględnia ciśnienie promieniowania fali wywierane na obiekt. Przewidywania Maxwella zostały potwierdzone w 1903 roku przez Nicholsa i Hulla poprzez precyzyjny pomiar ciśnienia promieniowania za pomocą wagi skrętnej. Przyrząd pomiarowy miał zwierciadła zawieszone na włóknie umieszczonym w szklanym pojemniku. Nichols i Hull uzyskali niewielkie, mierzalne odchylenie zwierciadeł od świecenia światła na jedno z nich. Na podstawie zmierzonego ugięcia obliczyli niezrównoważoną siłę działającą na lustro i uzyskali zgodność z przewidywaną wartością siły. Ciśnienie promieniowania wywierane przez falę elektromagnetyczną na doskonale pochłaniającą powierzchnię okazuje się równe gęstości energii fali. Załóżmy, że materiał doskonale odbija światło, a fale elektromagnetyczne padają prostopadle do powierzchni. W takim przypadku wywierane ciśnienie jest dwukrotnie większe, ponieważ po odbiciu kierunek pędu ulega odwróceniu.

Ciśnienie promieniowania odgrywa rolę w wyjaśnianiu wielu obserwowanych zjawisk astronomicznych, w tym pojawiania się komet. Kiedy kometa zbliża się do Słońca, nagrzewa się, a jej powierzchnia złożona z zamarzniętych gazów oraz cząstek skał i pyłu wyparowuje. Koma komety to zamglony obszar wokół niej złożony z gazów i pyłu. Część gazów i pyłu opuszczając kometę tworzy warkocze. Ogon jonowy składa się głównie ze zjonizowanych gazów. Jony te oddziałują elektromagnetycznie z wiatrem słonecznym, ciągłym strumieniem naładowanych cząstek emitowanych przez Słońce. Siła wiatru słonecznego działającego na zjonizowane gazy jest na tyle duża, że ogon jonowy prawie zawsze jest skierowany bezpośrednio w stronę przeciwną do Słońca. Drugi ogon składa się z cząstek pyłu. Ponieważ ogon pyłowy jest elektrycznie obojętny, nie oddziałuje z wiatrem słonecznym. Jednakże na ogon ten wpływa ciśnienie promieniowania wytwarzanego przez światło słoneczne. Chociaż ciśnienie to jest stosunkowo małe, jest wystarczająco silne, aby spowodować przemieszczenie ogona pyłowego z ścieżki komety.

Pęd i ciśnienie promieniowania

Obiekt absorbujący falę elektromagnetyczną doświadczyłby siły w kierunku rozchodzenia się fali. Ta siła występuje, ponieważ ...

Education

JoVE Core

Physics

Fizyka

Unit 1

Jednostka 1

Electromagnetic Waves

Fale elektromagnetyczne

KEY TERMS AND CONCEPTS

Kluczowe terminy i pojęcia

radiation pressure in light and comets

Radiation pressure is the force that electromagnetic waves can exert on matter. It appears because light carries momentum, so an object that absorbs a wave feels a push in the direction the wave travels. This same force helps explain why sunlight can affect small particles in space.

Maxwell predicted radiation pressure, and Nichols and Hull confirmed it in 1903. They used a torsion balance with mirrors suspended from a fiber inside a glass container. When they shone light on one mirror, the mirrors shifted slightly. From that tiny deflection, they calculated the unbalanced force and found agreement with the predicted value.

The size of the pressure depends on the surface. For a perfectly absorbing surface, the radiation pressure equals the energy density of the wave. For a perfectly reflecting surface with the wave hitting straight on, the pressure is twice as large because the light reverses momentum when it reflects.

Radiation pressure also helps explain comet tails. When a comet nears the Sun, it warms up and releases frozen gases, rock, and dust. This forms a coma, which is the hazy cloud around the comet, and it can also create tails.

The ion tail is made mostly of ionized gases. These ions interact with the solar wind, a stream of charged particles from the Sun, and the tail usually points away from the Sun. The dust tail is different. It contains neutral dust, so it does not respond to the solar wind. Instead, sunlight’s radiation pressure pushes the dust tail away from the comet’s path.

Radiation Pressure in Light and Comets

electromagnetic waves

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Maxwell’s equations explain how electric and magnetic fields work together to create electromagnetic waves. James Clerk Maxwell brought together the ideas of Oersted, Coulomb, Gauss, and Faraday and built a single theory of electromagnetism. Together with the Lorentz force law, his equations describe the laws of electricity and magnetism. A key part of Maxwell’s work is the symmetry in the equations. Faraday’s law shows that a changing magnetic field produces an electric field. Maxwell added...

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momentum and radiation pressure

Radiation pressure is the force that electromagnetic waves can exert on matter. It appears because light carries momentum, so an object that absorbs a wave feels a push in the direction the wave travels. This same force helps explain why sunlight can affect small particles in space. Maxwell predicted radiation pressure, and Nichols and Hull confirmed it in 1903. They used a torsion balance with mirrors suspended from a fiber inside a glass container. When they shone light on one mirror, the...

radiation pressure: problem solving

Radiation Pressure in Light and Space

Radiation pressure is the push that light can exert on matter. When an electromagnetic wave is completely absorbed by a surface, its energy density is transferred as momentum to that surface. The rate of momentum transfer on a surface perpendicular to the wave gives the force, and the force per unit area is the radiation pressure. A perfectly absorbing surface receives this pressure directly from the incoming wave. If the surface is perfectly reflecting, such as a metal surface, and the light...

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key terms and concepts

Explore how light carries momentum, creates radiation pressure, and was measured by Nichols and Hull. See how it helps shape comet tails.

Radiation Pressure in Light and Comets | JoVE K12

physics

JoVE Core Physics introduces the theory and application of fundamental physics topics, including kinematics, dynamics, fluid mechanics, statics, waves, and acoustics, with concise and easy-to-understand animated videos. Additionally, the scientist-in-action videos demonstrate the application of related concepts in classical and original research experiments performed in today's laboratories worldwide.

Weather and Climate

3.3.9-12.E

Physical Science

Waves and Electromagnetic Radiation

3.2.9-12.V

Louisiana Student Standards for Science

High School

Earth Science

Earth’s Systems

HS-ESS2-1

HS-ESS2-4

waves-and-their-applications-in-technologies-for-information-transfer

Waves And Their Applications In Technologies For Information Transfer

HS-PS4-1

Virginia  Standards of Learning

HIgh School

PS.7

PS.7.a

Alabama Course of Study Science

Waves and Their Applications in Technologies for Information Transfer

9-12.PS.2.2.e

9-12.P.3.7.c

Florida Department of Education

SC.912.P.10

SC.912.P.10.19

south-carolina-college-and-career-ready-science-standards

South Carolina College and Career Ready Science Standards

P-PS4-4

Earth and Space Science (ESS)

Earth’s Place in the Universe

E-ESS1-2.

E-ESS2-4.

new-york-state-science-learning-standards

New York State Science Learning Standards

HS. Waves and Electromagnetic Radiation

HS-PS4-4.

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3.3.9-12.L

Radiation Pressure in Light and Comets

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